The present study addresses the cerebral support for the mechanism of error detection (ED) operating during conscious execution of incorrect actions (deceptions) and in the resting state. Local cerebral blood flow was measured by positron emission tomography (PET), and demonstrated involvement of the anterior cingulate gyrus in processes associated with conscious deception. The data obtained here showed that ED operates in persistently executed errors - conscious control of ED was shown to be impossible. The hypothesis that failure of ED is an important factor in the formation of obsessive-compulsive disorder (OCD) was supported by analysis of PET data on the rate of glucose metabolism in the state of operative rest. Normative data from healthy subjects were compared with results obtained from patients with diagnoses of OCD and Tourette's syndrome. Patients showed decreases in glucose metabolism in the anterior cingulate gyrus, which can be regarded as a reflection of abnormal functioning of the cerebral ED system.